Lapping machine truing ring and fixture



A il 2, 19 3 s. A. BOETTCHER ET AL 3,375,614

LAPPING MACHINE TRUING RING AND FIXTURE Filed Dec. 9, 1964 3 Sheets-Sheet 1 ,Sigahenlfioda fimasA/ir BY [g A il 2, 1968 I s. A. BOETTCHER ET AL 3,375,614

LAPPING MACHINE TRUING RING AND FIXTURE Filed Dec. 9, 1964 3 Sheets-Sheet 2 58 dimes/U57 BY j April 2, 1968 s. A. BOETTCHER ET AL 3,375,614

7 LAPPING MACHINE TRUING RING AND FIXTURE 3 Sheets-Sheet Filed Dec.

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United States Patent 3,375,614 LAPPING MACHINE TRUING RING AND FIXTURE Stephen A. Boettcher, Deerfield, and James N. Farley,

Palatine, Ill., assignors to Speedfam Corporation, a corporation of Illinois Filed Dec. 9, 1964, Ser. No. 416,989 1 Claim. (CL 51-129) Our present invention relate-s to a truing and retaining ring and associated fixture means for predetermining the extent of lapping of work pieces positioned on a rotating lapping disc of a lapping machine.

The general type of lapping machine with which our present invention may be used includes a lapping disc, which'is rotatably driven about a vertical axis, and on which truing and retaining rings rest. These rings, which are free to rotate on their own axes, serve to hold work pieces within them against movement with the lapping disc, and to wear the lapping surface for maintaining it in planar condition. Located within each truing and retaining ring is .a plate for bearing on the work pieces.

It is an object of our present invention to provide a truing and retaining ring member, a plate member disposable therein for bearing on the work pieces, and means carried by one of the members and being engageable with the other of the members for arresting the downward movement of the plate member upon completion of the desired amount of lapping, whereby the lapping is auto matically discontinued without stopping the lapping disc.

In one embodiment of our present invention the plate member serves to carry stop means engageable with the top surface of the truing and retaining ring. More particularly, upwardly extending post members, which have radial arm portions overlying the top surface of the truing and retaining ring, are secured to the plate member, and adjustable stop means are mounted in the arm portions for engaging the top surface of the truing and retaining ringto arrest the downward movement of the plate member. The stop means may be either in the form of adjustable screw means or in the form of adjustable micrometer means.

As. a feature of our present invention, the above-described embodiment of lap limiting fixture may have associated therewith a dial indicator having a plunger engageable with the top surface of the truing and retaining ring to indicate the position of the plate member relative to the truing and retaining ring.

In another embodiment of our present invention the truing-and retaining ring serves to carry stop means which is engageable by the plate member. The stop means, which are mounted in the walls of the truing ring, may be In the drawings:

FIGURE 1 is a perspective view of a typical lapping machine with which the devices of our present invention may be associated;

FIGURE 2 is a partial vertical sectional view, on an enlarged scale, taken substantially along the line 22 in FIGURE 1, looking in the direction indicated by the arrows, and shows one embodiment of truing and retaining ring and associated fixture means of our present invention in operative position on the lapping disc;

FIGURE 3 is a bottom View, on a further enlarged scale, of the truing and retaining ring and lap limiting fixture shown in FIGURE 2;

FIGURE 4 is a fragmentary view, partly in section and partly in elevation, of a modified embodiment of lap limiting fixture of our present invention;

FIGURE 5 is a fragmentary view, partly in section 'and partly in elevation, of a further modified embodiment of lap limiting fixture of our present invention;

FIGURE 6 is a plan view of another embodiment of truing and retaining ring having rotatable stop members mounted in the walls thereof;

FIGURE 7 is a partial vertical median sectional view of the truing ring of FIGURE 6, associated with a plate member, in operative position on a lapping disc;

FIGURE 8 is an enlarged fragmentary vertical sectional view of the truing ring and rotatable stop member of FIGURE 7;

FIGURE 9 is an enlagred and elevational view of the rotatable stop member of FIGURE 8;

FIGURE 10 is a vertical median sectional view of a modified embodiment of truing and retaining ring having vertically adjustable stop members in the walls thereof; and

FIGURE 11 is a fragmentary horizontal sectional view, taken substantially along the line 1111 in FIGURE 10, looking in the direction indicated by the arrows.

Referring now to FIGURE 1, there is indicated generally by the reference numeral 10 a typical lapping machine with which the devices of our present invention may be associated. The lapping machine 10 includes a framework with a tubular base or housing 12 which provides support for a horizontal lapping disc '14 comprised of a plurality of segments 15 secured to a lap wheel 16 (FIGURE 2). A staging table 17 surrounds the lapping disc. Selective rotation of the lapping disc 14 about a either in the form of rota-table stop members having eccentric radially inwardly extending arm portions or in the form of vertically adjustable stop members having radially inwardlyextending arm portions.

'It is a further object of our present invention to provide a truing and retaining ring wherein the lower surface thereof is defined, atleast in part, by wear resistant material. By reason of this construction, the bottom surface of the truing and retaining ring is not subjected to wear as the latter serves to dress the lapping disc. Therefore, the distance between the top surface, or stop means, and the bottom surface of the truing ring remains constant, and the top surface, or stop means, of the ring may be used as an accurate reference surface for limiting lapping in accordance with the principles of our present invention.

Now in order to acquaint those skilled in the art with the manner of constructing and using truing and retaining rings and lap limiting fixture means in accordance with the principles of our present invention, we shall describe in connection with the accompanying drawings, preferred embodiments of our invention.

vertical axis is effected by drive means (not shown) mounted within the housing 12. Suitably secured to the opposite sides of the housing 12 are the lower ends of yertical columns 18. Extending between the upper ends of the columns 18, above the lapping disc 14, is a horizontal bridge member 20 provided with transverse arms 22 which number four in the particular lapping machine herein disclosed. Mounted at the outer ends of each of the transverse arms 22 is a vertical pneumatic piston and cylinder assembly indicated generally by the reference numeral 24. Each of the pneumatic assemblies 24 includes a cylinder 26 and a piston rod 28.

Associated with each of the piston-rods 28 is a lap limiting fixture 30 which, as best shown in FIGURES 2 and '3, comprises a horizontal pressure plate 32 having suitable connection with the lower end of the adjacent piston rod 28. Secured to and extending upwardly from the plate 32 adjacent the periphery thereof are a plurality of circumfe-rentially space-d post members 34 which preferably number three. The post members 34 have radially outwardly extending arm portions 36 which threadingly receive vertical adjustable stop screws 38 adapted to be locked in predetermined positions by retaining nuts 40. The lap limiting fixtures 30 are vertically movable with the piston rods 28. Raising of the fixtures 30 is effected by introducing air under pressure into the lower ends of the cylinders 26, while lowering of the fixtures 30 is effected by relieving the air pressure at the lower ends of the cylinders 26 and introducing air under pressure into the upper ends thereof.

The pressure plate 32 of each fixture 30 is adapted to fit, with slight clearance, within a truing and retaining ring 42. The ring 42, as shown in FIGURES 2 and 3, comprises an annular body portion 44 having a top surface 46 and a bottom surface 48. Formed in the bottom surface 48 is an annular recess 50 in which is mounted, as by an epoxy cement, a plurality of circumferentially spaced rectangular inserts or pad members '52. The pad members 52 must be fabricated of a material having a greater abrasion resistance than the material of the lapping disc 14 and are preferably formed of high wear resistant material such as boron carbide. The bottom surface 48 of the ring 42, and the lower coplanar faces of the pad members 52, are engageable with the lapping surface of the lapping disc 14, while the top surface 46 of the ring 42 underlies the arm portions 36 of the post members 34 and is engageable by the lower ends of the adjustment screws 38.

After the fixture screws 38 have been vertically adjusted and locked in place, work pieces 54 are confined within the truing and retaining ring 42 and moved into position beneath the pressure plate 32. With the pressure plate 32 bearing against the work pieces, the lower ends of the screws 38 are initially spaced from the top surface 46 of the ring 42. The amount of material that will be removed from the work pieces is determined by the initial distance between the lower ends of the fixture screws 38 and the top surface 46 of the ring 42. correspondingly, the ultimate vertical dimension of the work pieces 54 is determined by the difference between (a) the height of the ring 42 and (b) the preadjusted perpendicular distance from the plane of the lower ends of the fixture screws 38 to the plane of the lower face of the pressure plate 32.

As the lapping disc 14 is rotated, a freely flowing mixture of abrasive particles and an oil carrier is fed to the lapping disc 14 through discharge tubes 56 (FIGURE 1). A thin film 58 of this abrasive mixture (the thickness of which has been exaggerated in FIGURE 2 for purposes of clarity) covers the lapping surface of the lapping disc 14, and during the lapping operation the t-ruing and retaining ring 42 and the work pieces 54 ride on the film 58. Also, during the lapping operation, air under pressure introduced into the upper end of the corresponding cylinder 26 serves to impose through a piston rod 28 a downward force or pressure on the pressure plate 32 and, in turn, on the work pieces 54 for increasing the rate of lapping of the latter; and the ring 42 rotates relative to the pressure plate 32 about the axis defined by the piston rod 28 whereby the pad members '52 dress the lapping disc 14 for maintenance of its planar condition. As lapping of the work pieces proceeds, the lower ends of the screws 38 move to the top surface 46 of the ring 42.

When the lower ends of the screws 38 engage the top surface 46 of the ring 42, downward movement of the plate 32 is arrested and lapping of the work pieces 54 ceases automatically even though operation of the lapping machine continues. Because of the provision of the wear resistant pad members 52, the bottom surface of the truing and retaining ring 42 is not subjected to wear as the latter serves to dress the lapping disc 14. Therefore, the height of the ring 42 remains constant, and the top surface 46 serves as an accurate reference surface for the lap limiting fixture 30. All four sets of fixtures 30 and rings 42 are of the same construction and operation.

Referring now to FIGURE 4, there is indicated generally by the reference numeral 30a part of a modified embodiment of lap limiting fixture of our present invention. The fixture 30a is identical in construction and operation to the fixture 30 except that the adjustment screws 38 and lock nuts 40 at each of the three post members 34 are replaced by vertically disposed micrometers 60. Each of the micrometers 60 comprises a graduated sleeve 62 secured to the arm portion 36 of the post member 34, a spindle 64 that extends through the arm portion 36 and is engageable with the top surface 46 of the truing and retaining ring 42 for arresting downward movement of the plate 32, and a barrel 66 thatis rotatable for effecting vertical adjustment of the spindle 64.

Referring now to FIGURE 5, there is indicated generally by the reference numeral 30b part of a further modified embodiment of lap limiting fixture of our present invention. The fixture 30b, which may be otherwise similar to either of the fixtures 30 or 30a, includes an additional post member 34' having an arm portion 36' to which is secured a dial indicator or dial-gauge 68. The spindle 70 of the indicator 68 extends through the arm portion 36' and is engaged with the top surface 46 of the truing and retaining ring 42 for indicating the position of the plate 32 relative to the ring 42 and hence the thickness of material remaining to be removed from the work pieces 54 during the lapping operation.

In FIGURES 6 through 9, there is indicated generally by the reference numeral 72 another embodiment of truing and retaining ring of our present invention. The ring 72 comprises an annular body portion 74 having-three circumferentially spaced apart series of radial cylindrical openings 76a-j, 77a-f and 78a-j formed therethrough with the openings of each series being helically spaced apart. Corresponding openings of the three series, for example openings 76a, 77a and 78a, are at the same height and are spaced 120 degrees apart.

Disposed in one opening of each series of openings 76:44, 77a-f and 7811- is a generally cylindrical radially expandable stop member 80. Each of the stop members 80 has an eccentric arm portion 82 projecting radially inwardly of the body portion 74,.a tapered longitudinal threaded aperture 84 relieved as by slots 86 to permit radial expansion of the stop member, and a socket 88. Threadable in each of the apertures 841is a tapered threaded plug 90 having a socket 92 therein. The sockets 88 and 92 may be of hexagonal configuration and are adapted toreceive a socket wrench or the like.

Formed in the bottomsurface 94 of the body portion 74 is an annular recess 96 in which is mounted, as by an epoxy cement, a plurality of circumferentially spaced rectangular inserts or pad members 98. The pad members 98, like the pad members 52, must be fabricated of a material having a greater abrasion resistance than the material of the lapping disc 14 and are preferably formed of high wear resistant material such as boron carbide. The bottom surface 94 of the ring 72, and the lower coplanar faces of the pad members 98, are engageable with the horizontal lapping surface of the annular lapping disc 14 of a conventional lapping machine. The lapping disc is comprised of segments 15 secured to a lap wheel 16.

When using the truing ring 72,'the three stop members 80 are first disposed in one set of corresponding openings at a common level, for example openings 76a, 77a and 78a, to locate the eccentric arm portions 82 at the approximate desired height. Then, the stop members 80 are each rotatably adjusted, by a socket wrench inserted in the socket 88, until the eccentric arm portion 82 is at the precise desired height, Finally, each plug member 90 is threaded inwardly of the opening 84, by means of a socket wrench inserted in the socket 92, for radially expanding the stop members 80 whereby to lock the latter in the preselected angular positions within the openings 76a, 77a and 78a.

After the arm portions .82 of the stop members 80 have been suitably adjusted and locked in place, work pieces 100 are confined within the truing and retaining ring 72 beneath a pressure plate 32 having connection in a conventional manner with a pneumatically or hydraulically actuated piston rod 28. With-the pressure plate 32 bearing against the work pieces, the lower face of the pres sure plate is initially spaced from the upwardly facing surfaces of the eccentric arm portions 82 of the stop members 80. The amount of material that will be removed from the work pieces 100 is determined by the initial distance between the lower face of the pressure plate 32 and the arms 82. correspondingly, the ultimate vertical dimension of the work pieces 100 is determined by the distance between the plane of the upwardly facing surfaces of the arm portions 82 and the lapping surface of the lapping disc 14.

As the lapping disc 14 is rotated, a freely flowing mixture of abrasive particles and an oil carrier is fed to the lapping disc 14. A thin film 106 of this abrasive mixture (the thickness of which has been exaggerated in FIGURE 7 for purposes of clarity) covers the lapping surface of the lapping disc 14, and during the lapping operation the truing and retaining ring 72 and the work pieces 100 ride on the film 106. Also, during the lapping operation a downward force or pressure may be imposed through the piston rod 28 on the pressure plate 32 and, in turn, on the work pieces 100 for increasing the rate of lapping of the latter; and the ring 72 rotates relative to the pressure plate 32 about the axis defined by the piston rod 28 'whereby the pad members 98 dress the lapping disc 14 for maintenance of its planar condition. As lapping of the work pieces proceeds, the lower face of the pressure plate 32 moves closer to the stop arms 82.

When the lower face of the pressure plate 32 engages the stop arms 82, downward movement of the plate 32 is arrested and lapping of the work pieces 100 ceases automatically even though operation of the lapping machine continues. Because of the provision of the wear resistant pad members 98, the bottom surface of the ring 72 is not subjected to wear as the latter serves to dress the lapping disc 14. Therefore, the distance between the stop arms 82 and the bottom face of the ring 72 remains constant, and the stop arms 82 serve as accurate lap limiting references for the pressure plate 32. Adjustments in the vertical heights of the stop arms 82 may be made by transferring the stop members 80 from one set of corresponding openings 76af, 77a-f and 78a-f at one level to another set of corresponding openings at a different level, or by rotating the stop members 80 within the openings at a given level, or by a combination of both. A combined truing ring and lap limiting fixture 72 may be used at one or more lapping stations circumferentially spaced about the lapping disc 14.

Referring now to FIGURES and 11, there is indicated generally by the reference numeral 108 a modified embodiment of truing and retaining ring of our present invention. The ring 108 has an annular body portion 110 with three vertical slots 112 formed in the inner periphery thereof and spaced 120 degrees apart. Slidably mounted in each of the slots 112 is a stop member 114 having an arm portion 116 projecting radially inwardly of the body portion and having a slot 118 with an intermediate recessed shoulder 119. Extending through the slot 118 of each stop member 114 and threaded into an opening 120 in the truing ring body 110 is a bolt or screw 122 having a head portion engageable with the slot shoulder 119. The slots 118 accommodate vertical sliding movement of the stop members 114 relative to the bolts 122, and the stop members may be vertically adjusted by loosening the bolts 122, moving the stop members to the desired corresponding positions and tightening the bolts. The bottom surface 124 of the ring 110 is formed with an annular recess 126 in which is mounted a plurality of circumferentially spaced rectangular inserts or pad members 128. The inserts 128 are fabricated of the same material and are mounted and arranged in the same fashion as the inserts 98 of the truing and retaining ring 72, The described truing ring and lap limiting fixture means 108 is used in the same manner as the truing ring and lap limiting fixture means 72, with the stop arms 116 serving, in the same 'way as the stop arms 82, to limit downward movement of the pressure plate 32.

While we have shown and described what we believe to be preferred embodiments of our present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of our invention.

We claim:

1. For use in a lapping machine for predetermining the extent of lapping of work pieces on a rotating lapping disc, the combination of a truing and retaining ring normally resting on the lapping disc and having an annular body portion for confining work pieces therein and having an annular recess formed in the bottom surface of said body portion, a plurality of circumferentially spaced rectangular pad members of wear resistant material mounted within said annular recess and engageable with the lapping disc, a plate within and independent of said truing and retaining ring and bearing on the work pieces, a plurality of circumferentially spaced post members extending upwardly from said plate and having radial arm portions overlying the top surface of said truing and retaining ring, and micrometers carried by said arm portions of said post members and having adjustable spindles for engaging the top surface of said truing and retaining ring to arrest downward movement of said plate.

References Cited UNITED STATES PATENTS 2,971,298 2/1961 Garthwaite 51-13l 2,979,868 4/1961 Emeis 51-131 2,983,086 5/1961 Chapelle 51131 X 3,233,370 2/1966 Best 51-131 HAROLD D. WHITEHEAD, Primary Examiner. 

1. FOR USE IN A LAPPING MACHINE FOR PREDETERMINING THE EXTENT OF LAPPING OF WORK PIECES ON A ROTATING LAPPING DISC, THE COMBINATION OF A TRUING AND RETAINING RING NORMALLY RESTING ON THE LAPPING DISC AND HAVING AN ANNULAR BODY PORTION FOR CONFINING WORK PIECES THEREIN AND HAVING AN ANNULAR RECESS FORMED IN THE BOTTOM SURFACE OF SAID BODY PORTION, A PLURALITY OF CIRCUMFERENTIALLY SPACED RECTANGULAR PAD MEMBERS OF WEAR RESISTANT MATERIAL MOUNTED WITHIN SAID ANNULAR RECESS AND ENGAGEABLE WITH THE LAPPING DISC, A PLATE WITHIN AND INDEPENDENT OF SAID TRUING AND RETAINING RING AND BEARING ON THE WORK PIECES, A PLURALITY OF CIRCUMFERENTIALLY SPACED POST MEMBERS EXTENDING UPWARDLY FROM SAID PLATE AND HAVING RADIAL ARM PORTIONS OVERLYING THE TOP SURFACE OF SAID TRUING AND RETAINING RING, AND MICROMETERS CARRIED BY SAID ARM PORTIONS OF SAID POST MEMBERS AND HAVING ADJUSTABLE SPINDLES FOR ENGAGING THE TOP SURFACE OF SAID TRUING AND RETAINING RING TO ARREST DOWNWARD MOVEMENT OF SAID PLATE. 